An important parameter for HIV vaccines is the strength of CTL responses it elicits. Optimal induction of CTL response requires at least two types of biological signals. Signal 1 is provided by antigenic peptide presented by MHC class I molecules. Costimulatory molecules, the prototypes of which are CD80 family members CD80 and CD86, deliver signal 2. While costimulatory activity can be conferred by expression of a single gene such as CD80, generation of antigenic signals for CTL requires co-ordinated expression of multiple genes, such as proteosome components LMP-2, LMP-7, transporter TAP-1, TAP-2, MHC class I heavy chain, and beta 2 microglobulin, in addition to the nominal antigen. This has made it difficult to design a vector that delivers both signals for T cell activation. The applicant has found that the proto-oncogene, PML, controls multiple genes devoted to MHC class I antigen-presentation. This finding makes possible the design of novel constructs that enable co-delivery of both signals to induce anti-HIV CTL responses. The central theme of the current pilot study is to design DNA vaccines that allow the MHC class I-low recipient cells to present both signal 1 and signal 2, and to test if these types of vaccines are superior to conventional DNA vaccines in inducing anti-HIV CTL responses. Specifically, the following questions will be addressed: 1. Can DNA vector and/or recombinant adenovirus-associated virus be produced that efficiently induce expression of HIV antigen, costimulatory molecules and multiple antigen presenting genes, such as LMP2/7 and TAP1/2? The applicant will co-express costimulatory molecule CD80, an HIV gp120 antigen epitope and the proto-oncogene PML that controls multiple genes devoted to antigen presentation. 2. Can both effector and memory T cells specific for an HIV gp120 CTL be induced? The effect of co-delivery of both antigenic and co-stimulatory signals in the induction of anti-HIV CTL responses will be tested. Should co-delivery of signals 1 and 2 induce better protection, then an expanded proposal will be submitted to evaluate the potential of this approach in the development of a vaccine for HIV/SIV infection in primates and humans.